`map_data/src/fileformats.py` imports nonexistent `fileicon` from `core.files`

[zjp]

core.utils has a set_file_icon function -- is that the new version?

[tomgoddard]

The code with the wrong import location of set_file_icon is unported code from an early version of ChimeraX called Hydra. Maybe should remove that unported code, but it needs evaluation since it may be something we want. Low priority.